looks like I am not the only one trying to figure out this P1515 code as well... When I run the foxwell, I get a 2B70, 2B71 and 2B72 dtc code that leads to something indicating "plausibility" and a bmw tech indicated I needed a new DISA aka Drive unit located at the back on the intake...

the P1515 code all over the BMW forums points to TPS/TB and was recently advised from someone on here to clean the TB thoroughly, clear code and run car...

so for now, a TB clean, although may or may not fix my issue, will not cost me much and shouldn't hurt.

my 4.8is currently drives fine to me.

anyone have better luck?

bit of backstory - I did swap out a dead battery to a AGM duralast from autozone and the code did pop up shortly after. I was able to clear it one time, and it didn't come back for a couple of days.. now I clear it and it pops right back up.

prior to installing the new battery, she was jumped correctly but she did idle surge a few times before the battery completely gave out.

__________________
2006 4.8is TIAG/BLACK